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    <title>Document</title>
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<script>
    /* 
        1.使用Boolean函数来将其他类型转换为布尔值
            -  0  false NaN  '' null  undefined  转布尔值都是false
        -所有表示空性的没有的错误的值都会转换为false
    */
   let a;
    a =  Boolean(a)
   console.log(a);
   if(null){
    console.log('000');
   }
</script>
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